1. Field of the Invention
The present invention relates to a coating composition containing a combination of polymer-bound ultraviolet light absorbing compounds.
2. Discussion of the Prior Art
Ultraviolet absorbers are used in coating compositions to reduce the degradation of the coating resulting from the effects of atmospheric oxygen, moisture and ultraviolet light. The degradation is manifest in cracking, loss of gloss, changes in shade, delamination and formation of bubbles in the cured coating films. It is known that stabilizers, such as ultraviolet (uv) absorbers, substantially prevent or minimize such damage in coatings.
Examples of ultraviolet light absorbers include benzotriazoles, 2-hydroxybenzophenones oxanilide, and 2-hydroxyphenyltriazines. Benzotriazoles are highly effective ultraviolet light absorbers over a broad spectrum, but these compounds are often not stable and may migrate to other coating layers in a multi-layer coating system or may chemically degrade in the coating composition, thereby losing efficacy as ultraviolet light absorbers. Triazine ultraviolet absorber compounds are more chemically stable, but do not have the range of ultraviolet light absorption that the benzotriazoles have.
It is an object of the present invention to improve the stability of ultraviolet light absorbers in a coating composition, to enhance ultraviolet light absorption and to reduce degradation of a coating composition due to ultraviolet light exposure.